How to Build A Cold Frame

Well folks, it’s that time of year again when gardens are flourishing with the bounties of the early and late spring plantings and I am beginning to plan for my first attempt at season succession. A cold frame has been heavily considered to help extend the seasons in my garden throughout the colder months.

Cold frames, in essence, can be made from various items – namely, straw bails, old wood and other rigid materials. One of the more important aspects is a transparent sash (lid) to allow the absorption of solar energy, which can greatly influence production within the cold frame. These devices help to keep harsher weather away from one’s crops, such as heavy snowfall, rainfall, excessive wind and so forth. In addition, a cold frame can help to allow the year-round gardener to grow less resilient vegetables a little earlier in the season, given its inherent protection from the elements. It can often be used to start seedlings and/or harden vegetables before transplanting.

As part of this investigation, a few of us looked into some different designs, keeping in mind that we wanted to use recycled materials whenever possible, and that the design needed to stay simple: complexity in a cold frame is certainly unnecessary. This design has been created to use recycled windows, which can be easily sourced; within Halifax, Renovators Resource is a fine place to find old windows for $10 or more, along with recycled hinges, handles and such. Although we highly recommend the use of sustainably harvested hemlock or cedar (rot resistant wood types), there are other sustainable manufacturers of less resilient woods like spruce and fir. Within the pictures shown, we’ve used the latter; keep in mind that natural (chemical free) rot-resistant liquids can be applied to the wood before building to help mitigate rot. 

Below is a quick look at a 3-step design we’ve been using this summer to prepare our gardens for the next step.

1) Measure the window dimensions (don’t forget to measure twice!) and cut the frame wood. One can use 2×6 or 2×8 for the frame depending on how deep you would like the frame to be.

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2) Assemble the back of the frame using two pieces of 2×2 that are cut 1″ lower than the height of the back and space them inwards 1.5″ (planed wood) or 2″ (unplaned/rough wood); repeat this for the front. Attach the both sides of the frame to these pieces of 2×2. Remember, the back of the frame will be three tiers high and the front will be two tiers high. This creates a slope to maximize the absorption of solar energy; in addition, the last two pieces on each side will be cut with a slope to match the back and front of the frame.

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3)  With the frame assembled, attach the window to the frame using your recycled hinges, and test it to see if it opens easily and that the hinges are snug enough.

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And you’re done!

For more ideas on building cold frames, check out Niki Jabbour’s Book: The Year Round Vegetable Gardener for a clear step by step plan. If you don’t have access to tools, check out places like the Halifax Tool Library and learn how you can borrow tools without the expense and hassle of owning. You can also order pre-cut lumber if you don’t have access to a saw, or feel uncomfortable using certain tools.

For more info on using your cold frame, check out our post on How to Extend Your Garden Season.

Updated from posts originally published in 2013 and 2016

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